Method for controlling the deformation of a surface of a sail of a sailing boat during a direction change manoeuvre

ABSTRACT

There is described a method for controlling the deformation of a surface of a sail ( 1 ) of a sailing boat ( 100 ) during a direction change manoeuvre, said method comprising the step of arranging at least one inflatable batten ( 10 ) into a respective seat ( 3 ) formed on a side surface ( 2   a ) of the sail ( 1 ), said at least one batten ( 10 ) being inflated at a predetermined working pressure, said working pressure being such as to impart to said at least one batten ( 10 ) a bending stiffness having, with no bending load, a predetermined value and the step of carrying out a manoeuvre for changing the direction of the sailing boat ( 100 ), wherein in a first part of said manoeuvre said at least one batten ( 10 ) is subjected to the action of an increasing bending load and in a second part of said manoeuvre, said bending load ends its action on said at least one batten ( 10 ), during said manoeuvre the mechanical properties of said at least one batten ( 10 ) being changed so that as said bending load increases in said first part of the manoeuvre, the value of the bending stiffness of said at least one batten ( 10 ) decreases considerably, and as the action of said bending load ends in said second part of the manoeuvre, the bending stiffness of said at least one batten ( 10 ) returns to said predetermined value. Such method is carried out by using a sail ( 1 ) provided with at least one batten ( 10 ) comprising a fluid impervious wrapping ( 31 ) adapted to be inflated by a fluid under pressure and a reinforcing structure ( 33 ) associated externally with said wrapping ( 31 ) and comprising a plurality of reinforcing thread-like elements ( 34   a,    34   b ) arranged crossed with an angle comprised between about 65° and about 115°.

The present invention relates to a method for controlling thedeformation of a surface of a sail of a sailing boat during a directionchange manoeuvre, specifically a veer or a gybe.

The invention also relates to a sail for a sailing boat and to a battenfor such sail, such sail and such batten allowing the above method to becarried out.

Preferably, but not exclusively, the method is carried out by a crew ofa racing sailing boat, such as an America's Cup class boat. The sailsand the battens of the present invention are thus intended to bepreferably but not exclusively used on such type of boats.

Throughout the following description and appended claims, the word:veer, is used to indicate a direction change manoeuvre withsubstantially fore wind, adapted to bring the boat to get wind on theside opposite that where it gets wind before the manoeuvre is carriedout, while the word: gybe, is used to indicate a direction changemanoeuvre with substantially aft wind, adapted to bring the boat to getwind on the side opposite that where it gets wind before the manoeuvreis carried out.

As known, in sailing boats, especially in racing sailing boats, the useof sails provided with suitable stiffening battens is diffused; this isto improve the boat performance and speed during the race.

The sails provided with battens are, for example, the mainsail, thegenoa and the jib.

The battens are housed into respective seats or pockets formed on theside surfaces of the sails and have the function of imparting desiredbending stiffness and/or aerodynamic properties to the sails, whenunfurled, while offering at the same time the largest sail surface tothe wind. Typically the battens, in the top portion of the sails, allowforming the roach that allows to increase the surface of the sailexposed to the wind and thus to improve the boat performance and speed.

Specifically, in the genoa, the battens have the function of imparting adesired bending stiffness to the sails and of preventing the flapping ofthe after leech; in that case, therefore, the battens follow the sailprofile imposed by the wind, offering to the wind a sail surface aslargest as possible. Typically, four or five battens are used in thegenoa, of which at least three are arranged in the top portion of thesail, where the after leech has a strong roach, and one or two battensin the bottom portion of the sail, where the after leech is straighter.

In the mainsail, on the other hand, the battens have the function ofenhancing the sail aerodynamic properties imparting the desired shapethereto.

Generally, the battens used in the sails of racing sailing boats aremade of composite materials, such as resins reinforced with glass orcarbon fibres.

GB 2354218 discloses a stiffening batten for a sail, comprising aninflatable pipe provided with means for attaching to the sail edge. Theinflatable pipe is made, for wide sails, of reinforced elastomericmaterial and for small sails, of polymeric material, preferably PVC orpolyethylene.

WO 94/14648 discloses an inflatable sail batten, in particular for amainsail intended to be wound inside the boat mast. The batten isarranged in a special pocket formed on the sail. The batten consists ofa fluid-impervious flexible tube having sealed opposite ends. At one ofthese ends, a small tube communicating with the interior of the flexibletube is connected to a supply tube extending along the sail edge. Thesupply tube is connected to a valve for inflating the batten. Thefluid-impervious flexible tube of the batten consists of an inner layerof nylon or polyester coated with an outer layer of polyurethane;optionally, the tube may be made of polyurethane or rubber coated with awoven fabric.

The Applicant has studied how to control the deformation of the sailsurface during the veer and gybe maneuvers of sailing boats, inparticular of racing sailing boats, to minimise the boat speed losswhile the above maneuvers are carried out. Specifically, the Applicanthas evaluated the mechanical behaviour of the battens during the abovemaneuvers, aware of the critical role of such battens while suchmaneuvers are carried out.

The Applicant has noted, with special reference to the genoa, thatduring the veer and gybe maneuvers the sail is maneuvered to allow itsafter leech to pass from one side to the other of the sailing boat mast.During such passage, the battens hit the equipment of the boat mast,thus being subjected to the action of a bending load which is alwaysincreasing until the battens become deformed and are able to go beyondthe mast.

The Applicant has thus determined, as a critical element of the battensfor sailing boat sails, the fact that on the one side, they must offerthe desired features of bending stiffness to the sail, adapted to allowthe sail to get the wind thrust and on the other side, they must besufficiently flexible so as to not oppose high resistance to the sailpassage beyond the sailing boat mast during the above direction changemaneuvers, to then return, at the end of the manoeuvre, to offer thedesired bending stiffness features to the sail. Such battens, moreover,must be able to stand high fatigue stresses they are subjected to due tothe frequency of such maneuvers during the races.

In this perspective, the Applicant has verified that the battens of theprior art, while bending when subjected to a bending load due to theeffect of the thrust against the mast equipment during the veer and gybemaneuvers, still exhibit a high resistance to the passage of the battenbeyond the mast. This is due to the fact that they exhibit suchmechanical properties that their bending stiffness remains always highas the bending load increases while the manoeuvre is carried out.Moreover, the battens of composite material typically used on racingsailing boats, as the bending load increases, are subjected to ruptureby violent impact, excessive deformation or fatigue after a certainperiod of use.

The Applicant has found that it is possible to control the surfacedeformation of the sail of a sailing boat, during a direction changemanoeuvre, by using an inflatable batten having such mechanicalproperties that up to a predetermined value of the bending loaddetermined by the wind thrust on the sail, the bending stiffness remainssubstantially constant, whereas as the bending load increases due to thethrust against the mast equipment during the first part of the directionchange manoeuvre, the bending stiffness of the batten decreasesconsiderably, to then immediately return to the initial value, once thebatten has gone beyond the mast.

The present invention thus relates, in a first aspect thereof, to amethod for controlling the deformation of a surface for a sail ofsailing boat during a direction change manoeuvre, said method comprisingthe steps of:

arranging at least one inflatable batten into a respective seat obtainedon a side surface of a sail of a sailing boat, said at least oneinflatable batten being inflated at such a pressure as to impart to saidat least one inflatable batten a bending stiffness having, with nobending load, a predetermined value;

carrying out a direction change manoeuvre of the sailing boat, whereinin a first part of said manoeuvre said at least one batten is subjectedto the action of an increasing bending load and in a second part of saidmanoeuvre said bending load ends its action on said at least one batten,during said manoeuvre the mechanical properties of said at least onebatten being modified so that as said bending load increases in saidfirst part of the manoeuvre, the value of the bending stiffness of saidat least one batten decreases considerably and as said bending load endsits action in said second part of the manoeuvre, the bending stiffnessof said at least one batten returns to said predetermined value.

Advantageously, the use of a batten having mechanical properties which,while the direction change manoeuvre is carried out, change as describedabove, allows optimum control of the sail surface deformation duringsuch manoeuvre. Such batten, in fact, exhibits the advantageous featureof having a high initial bending stiffness up to a predetermined loadvalue. Said bending stiffness is obtained by the inflation pressure, thediameter and the elastic modulus of the materials making up the batten,so as to allow the sail to get the wind thrust in the best possible wayand to improve its behaviour as the wind intensity changes, offering tothe wind a sail surface as largest as possible. In any case, the highinitial stiffness does not hinder the execution of the direction changemanoeuvre; in fact, as the bending load on the batten increases, by theeffect of the thrust against the mast equipment, the value of the battenstiffness decreases up to reach very low values, and optionally becomesubstantially null when the bending load reaches a predetermined value,to then return immediately to the initial value when the battenstretches once it has gone beyond the mast.

In this way, the Applicant has obtained an excellent compromise betweenbending stiffness and flexibility. In particular, the substantialreduction of the bending stiffness as the bending load increases in thefirst part of the manoeuvre and the sudden return to the initialstiffness value in the second part of the manoeuvre allow carrying outthe manoeuvre in a time shorter than what it is possible to do with theprior art battens, thus enabling the boat to minimise the speed lossconsequent to the manoeuvre itself.

In a second aspect thereof, the present invention relates to a sail forsailing boats, comprising:

at least one seat for housing a respective batten;

at least one inflatable batten housed into said at least one seat, saidat least one inflatable batten comprising:

-   -   a fluid impervious wrapping containing a fluid under pressure so        as to impart a bending stiffness to said at least one batten,        said bending stiffness having, with no bending load, a        predetermined value;    -   a reinforcing structure associated with said wrapping,        preferably external thereto, and comprising a plurality of        reinforcing thread-like elements arranged crossed to each other        (preferably, as it will better be seen hereinafter, at a        predetermined angle comprised between about 65° and about 115°),        said at least one batten being such that, when subjected to an        increasing bending load, the bending stiffness thereof decreases        considerably and when said bending load ends its action, the        bending stiffness thereof returns to said predetermined value.

In particular, the Applicant has verified that a sail of the typedescribed above exhibits the desired features of bending stiffness, whenunfurled and of flexibility at the battens during the direction changemaneuvers.

More in particular, the above crossed arrangement of the reinforcingthread-like elements in the batten reinforcing structure imparts a highbending stiffness to the batten itself with no bending load and asubstantial decrease of such stiffness as the bending load increases.

In a third aspect thereof, the present invention relates to a batten forsails of a sailing boat, comprising:

a fluid impervious wrapping adapted to be inflated by a fluid underpressure, wherein such fluid under pressure imparts a bending stiffnessto said batten, said bending stiffness having, with no bending load, apredetermined value;

a reinforcing structure associated with said wrapping, preferablyexternal thereto, and comprising a plurality of reinforcing thread-likeelements arranged crossed to each other at a predetermined angle;

wherein, when said wrapping is inflated at said working pressure andsaid batten is subjected to an increasing bending load, the bendingstiffness thereof decreases considerably and when said bending load endsits action, the bending stiffness thereof returns to said predeterminedvalue.

The present invention, in at least one of the above aspects thereof,could exhibit the following preferred features.

According to preferred embodiments of the present invention, the valueof said bending stiffness decreases to be comprised between about 0.01%and about 50% of said predetermined value.

Even more preferably, the value of said bending stiffness decreases tobe comprised between about 0.01% and about 30% of said predeterminedvalue.

Even more preferably, the value of said bending stiffness decreases tobe comprised between about 0.01% and about 10% of said predeterminedvalue.

Even more preferably, the value of said bending stiffness decreases tobe comprised between about 0.01% and about 5% of said predeterminedvalue.

More preferably, for a bending load higher than a predeterminedthreshold value, the bending stiffness of said at least one batten issubstantially null.

In a preferred embodiment, the above predetermined value of bendingstiffness with no bending load is comprised between about 10 Nm² andabout 100 Nm².

Preferably, said batten is inflated at an operating pressure comprisedbetween about 5 bar and about 50 bar.

The bending stiffness of the batten depends, the batten diameter beingequal, on the inflating pressure of the batten itself. By changing thepressure in the above range of values, it is advantageously possible tomodulate the batten stiffness so as to obtain a good behaviour of thesail both with weak and with strong wind.

More preferably, the working pressure of the batten is comprised betweenabout 15 bar and about 50 bar for battens with an inner diametercomprised between about 20 mm and about 35 mm.

In a different preferred solution, the working pressure of the batten iscomprised between about 5 bar and about 30 bar for battens with adiameter comprised between about 35 mm and about 70 mm.

Such ranges of pressure values have been verified to be such as to allowoptimum behaviour of the sail both with weak and with strong wind.

According to preferred embodiments of the present invention, said battenis provided with a reinforcing structure comprising a plurality ofreinforcing thread-like elements arranged crossed to one another.

Preferably, the above reinforcing thread-like elements are arrangedcrossed at a predetermined angle comprised between about 65° and about115°.

Preferably, said predetermined angle is comprised between about 70° andabout 110°.

More preferably, said predetermined angle is comprised between about 80°and about 100°.

Even more preferably, said predetermined angle is substantially a rightangle.

Preferably, said at least one batten comprises a fluid imperviouswrapping containing a fluid at a working pressure.

Preferably, a reinforcing structure is associated with said wrapping,preferably outside thereto.

Preferably, said reinforcing structure is closed at the ends of saidbatten.

Advantageously, the Applicant has verified that a reinforcing structureof the type described above allows achieving the desired features ofbending stiffness and flexibility. In particular, the above crossedarrangement of the reinforcing thread-like elements of the battenimparts to the batten itself, for the different objects of the presentinvention, a high bending stiffness for low load values and asubstantial decrease of such stiffness up to a negligible orsubstantially null value as the bending load increases.

According to preferred embodiments of the present invention, saidreinforcing structure comprises a layer comprising first reinforcingthread-like elements arranged along a first direction and secondreinforcing thread-like elements arranged along a second directioninclined, relative to said first direction, by said predetermined angle.

According to further embodiments of the present invention, saidreinforcing structure comprises two overlapped layers of reinforcingthread-like elements, a first layer comprising first reinforcingthread-like elements arranged along a first direction and a second layercomprising second reinforcing thread-like elements arranged along asecond direction inclined, relative to said first direction, by saidpredetermined angle.

Preferably, said second reinforcing thread-like elements are arrangedparallel to one another along a substantially longitudinal direction ofsaid batten.

Preferably, said first reinforcing thread-like elements are arrangedparallel to one another along a substantially circumferential directionof said batten.

In an alternative embodiment of the batten of the present invention,said second reinforcing thread-like elements extend along respectivepaths having an angle of inclination comprised between about +20° andabout −20° relative to a longitudinal direction of said batten.

In a further alternative embodiment of the batten of the presentinvention, said first reinforcing thread-like elements extend alongrespective paths having an angle of inclination comprised between about+5° and about −5° relative to a circumferential direction of saidbatten.

Advantageously, for the various objects of the present invention, thereinforcing thread-like elements arranged along the circumferentialdirection of the batten (or along the above paths inclined relative tosaid direction) ensure the containment of the inflating pressure,whereas the reinforcing thread-like elements arranged along thelongitudinal direction of the batten (or along the above inclined paths)are adapted to contain the pressure acting in the axial direction andfor imparting the desired bending stiffness features. The Applicant hasverified that, advantageously, such a structure is particularlyadvantageous as it allows separating circumferential deformations fromlongitudinal ones.

Preferably, the layer of longitudinal reinforcing thread-like elementsis arranged external to the layer of circumferential reinforcingthread-like elements. The Applicant has verified that, advantageously,such arrangement allows maintaining the batten diameter during theinflation.

Preferably, said reinforcing thread-like elements preferably comprisecords made of kevlar or other material having a high modulus.

Such reinforcing thread-like elements are preferably incorporated in avulcanised elastomeric material, for example based on diene elastomerscharged with at least one reinforcing charge, for example carbon black.

According to preferred embodiments of the present invention, said atleast one batten comprises, at a first end thereof, a first closing cap.

Preferably, said at least one batten comprises, at a second end thereof,a second cap comprising an inflating/deflating valve.

Preferably, said first and second closing caps comprise a tubular sleevesealingly coupled to an inner surface of said fluid impervious wrapping.

Preferably, the reinforcing thread-like elements are connected to theabove first and second closing caps.

Even more preferably, the above reinforcing thread-like elements arelongitudinal reinforcing thread-like elements.

Preferably, said tubular sleeve is provided with a first sealing lip inabutment against a front end surface of said fluid impervious wrappingand a tubular collar sealingly coupled to an outer surface of saidreinforcing structure and to said sleeve. Such configurationadvantageously ensures that the desired working pressure is maintained.

Preferably, said inflating/deflating valve is associated with a frontsurface of said sleeve, said sleeve further comprising a protection lipfor said inflating/deflating valve. Such protection lip isadvantageously provided for preventing the accidental opening of thevalve during the introduction/removal of the batten into/from the sailseat and while the maneuvers are carried out, when the batten hitsagainst the mast equipment.

More preferably, said protection lip comprises a tapered side surface soas to reduce weight and overall dimensions.

According to preferred embodiments of the present invention, said battenhas a substantially tubular shape with circular section substantiallyconstant along the entire longitudinal extension thereof.

In a further alternative embodiment, said batten has a substantiallycylindrical shape wherein at least one end is tapered as a cone. In thisway it is possible to have a variable stiffness along the batten axis,thus allowing better shaping of the sail shape.

Preferably, said sail is a genoa or a mainsail.

Further features and advantages of the present invention will appearmore clearly from the following detailed description of a preferredembodiment, made with reference to the attached drawings. In suchdrawings:

FIG. 1 is a schematic side view of a sail according to the presentinvention;

FIG. 2 is a schematic, partly sectioned and cutaway view of a battenaccording to the present invention used in the sail of FIG. 1;

FIG. 3 is a schematic perspective view of a central portion of thebatten of FIG. 2, with an enlarged detail of a portion of the side wallthereof according to a preferred embodiment of the present invention;

FIG. 3 a is a schematic perspective view of a central portion of thebatten of FIG. 2, according to a further embodiment of the presentinvention;

FIG. 4 a is a view of a sail according to the present invention, used ona sailing boat in a step preceding the execution of a manoeuvre forchanging the direction of the sailing boat;

FIGS. 4 b, 4 c show the sail of FIG. 4 a in two consecutive steps of thedirection change manoeuvre;

FIG. 4 d shows the sail of FIG. 4 a at the end of the direction changemanoeuvre;

FIG. 5 shows a graph relating to the variation of the bending stiffnessbased on the bending load obtained by carrying out experimental tests onthree battens manufactured according to a preferred embodiment of thepresent invention;

FIG. 6 shows a graph relating to the variation of the bending stiffnessbased on the bending load obtained comparing a batten manufacturedaccording to a preferred embodiment of the present invention with abatten manufactured according to an alternative embodiment of thepresent invention;

FIG. 7 is a schematic view depicting a test for obtaining the bendingstiffness when the load changes as depicted in FIGS. 5 and 6.

In FIGS. 1 and 4 a-4 d, reference numeral 1 indicates a sail accordingto the present invention. The sail 1, in particular, is a genoa for aracing sailing boat, such as an America's Cup class boat.

Sail 1 comprises a composite fabric 2 of conventional shape andmaterial. On a side surface 2 a of the composite fabric a plurality ofseats or pockets is provided, all indicated by reference numeral 3,which house respective stiffening battens, all indicated by referencenumeral 10.

In the example shown in FIGS. 1 and 4 a-4 d, there are shown fivebattens 10 of different length arranged one on top of the other alongthe portion of sail 1 at after leech 4. In particular, three battens 10are arranged in the top portion of after leech 4, where the sail roachis larger and two battens 10 are arranged in the bottom portion of sail1, where the after leech 4 is straighter. Number, length and position ofbattens 10 may be different from what shown.

As shown in FIGS. 2 and 3, each batten 10 comprises a fluid imperviouswrapping 31 having substantially tubular shape and defining a chamber 32therein that contains a fluid under pressure.

Wrapping 31 is associated, preferably at the outer surface thereof, witha reinforcing structure 33, preferably by co-vulcanisation.

The fluid impervious wrapping 31 and the reinforcing structure 33 extendalong a longitudinal axis X-X of batten and preferably, have a circularcross section of constant diameter along such axis X-X.

As schematically shown in the enlargement of FIG. 3, the reinforcingstructure 33 comprises a plurality of reinforcing thread-like elements34 a, 34 b arranged, as already mentioned, according to a crossed layoutwith an angle comprised between about 65° and about 115°. In thepreferred embodiments of the batten of the present invention, the abovecrossed angle is comprised between about 70° and about 110°, morepreferably between about 80° and about 100°.

In a particularly preferred embodiment of the batten of the presentinvention, shown in FIGS. 2 and 3, the above crossed angle issubstantially a right angle.

As better shown in FIG. 3, the reinforcing structure 33 comprises twooverlapped layers of reinforcing thread-like elements, such layers beingrespectively indicated by reference numerals 33 a and 33 b. Layer 33 acomprises a plurality of reinforcing thread-like elements 34 a arrangedparallel to one another and extending along a circumferential directionof batten 10, whereas layer 33 b comprises a plurality of reinforcingthread-like elements 34 b arranged parallel to one another and extendingalong a longitudinal direction of batten 10. Layer 33 b is arrangedoutside layer 33 a and is associated with layer 33 a preferably byco-vulcanisation.

As already mentioned, in a first alternative embodiment (not shown), thereinforcing thread-like elements 34 a, rather than extending along acircumferential direction substantially perpendicular to thelongitudinal direction of the batten, deviate from the circumferentialdirection by an angle of inclination comprised between about +5° andabout −5° optionally following spiral paths.

In a second alternative embodiment, not shown, the reinforcingthread-like elements 34 b, rather than extending along a longitudinaldirection substantially parallel to axis X-X of batten 10, extend alongrespective paths having an angle of inclination comprised between about+20° and about −20 relative to the above longitudinal direction.

The fluid impervious wrapping 31 is preferably made with a substantiallyfluid impervious elastomeric material, for example butyl-based.

The reinforcing thread-like elements 34 a, 34 b are preferablyincorporated in an elastomeric material based on diene elastomerscharged with at least one reinforcing charge, for example carbon black.Moreover, such elastomeric material usually includes adhesive elements,adapted for promoting the adhesion between the elastomeric material andthe reinforcing thread-like elements, for example resorcinol and HMMM(examethoxymethylammine). Said reinforcing thread-like elementspreferably comprise cords made of kevlar or of any other high modulusmaterial. The fluid impervious wrapping 31 and layers 33 a and 33 b arevulcanised.

As already mentioned, in alternative embodiments (not shown) of batten10 of the present invention, the reinforcing structure 33 of batten 10consists of a single layer comprising the reinforcing thread-likeelements 34 a arranged along a substantially circumferential direction,or a direction that could deviate from to the circumferential directionby an angle of inclination comprised between about +5° and about −5°,optionally following spiral paths and the reinforcing thread-likeelements 34 b arranged along the longitudinal direction of batten 10(axis X-X) or along respective paths having an angle of inclination,relative to the longitudinal direction, comprised between about +20° andabout −20°.

At a first end 10 a thereof, batten 10 of the invention comprises aclosing cap 40 a (FIG. 2). Cap 40 a comprises a tubular sleeve 41 asealingly coupled to an inner surface of the fluid impervious wrapping31 and a tubular collar 42 a sealingly coupled to an outer surface ofthe reinforcing structure 33. In turn, sleeve 41 a comprises a sealinglip 43 a in abutment against a front surface of the fluid imperviouswrapping 31 and a front end surface 44 a. Collar 42 a, on the otherhand, comprises a sealing lip 45 a in abutment against the sealing lip43 a and housed in a seat 46 a formed in the sleeve 41 a between thesealing lip 43 a and the front end surface 44 a.

At the second end 10 b opposed to the first end 10 a, batten of theinvention comprises a closing cap 40 b almost similar to cap 40 a. Cap40 b therefore comprises a tubular sleeve 41 b sealingly coupled to aninner surface of the fluid impervious wrapping 31 and a tubular collar42 b sealingly coupled to an outer surface of the reinforcing structure33. In turn, sleeve 41 b comprises a sealing lip 43 b in abutmentagainst a front surface of the fluid impervious wrapping 31 and a frontend surface 44 b. Collar 42 b comprises a sealing lip 45 b in abutmentagainst the sealing lip 43 b and housed in a seat 46 b formed in thesleeve 41 a between the sealing lip 43 b and the front end surface 44 b.

The tubular collars 42 a, 42 b, are pressed until they become deformedonto the respective tubular sleeves 41 a and 41 b, so as to constrainthe fluid impervious wrapping 31 and the reinforcing structure 33comprising the above reinforcing thread-like elements 34 a, 34 b.

The closing cap 40 b further comprises an inflating/deflating valve 47associated, preferably screw-wise, with a seat 48 formed on the endsurface 44 b of sleeve 41 b. In order to protect such valve 47, sleeve41 b comprises a protection lip 49 projecting from the end surface 44 b.Such protection lip 49 has a cylindrical side surface 490 which istapered so as to impart to lip 49 the shape of a flute beak. Suchcylindrical surface 490 is open at the top thereof so as to allow accessto valve 47.

In the example shown, batten 10 has a tubular shape with circularsection substantially constant along the entire longitudinal extensionthereof. There are provided variations wherein the shape of batten 10 iscylindrical with at least one end tapered as a cone.

Battens 10 are advantageously used in the sails of racing sailing boats(see, for example, sail 1 illustrated in FIGS. 1 and 4 a-4 d) to impartthe desired bending stiffness to the latter and prevent the flapping ofthe after leech during the race. Such battens 10 follow the sail profileimposed by the wind, offering to the wind a sail surface as largest aspossible. In particular, battens 10, when used in the top portion of thegenoa, allow increasing the sail surface exposed to the wind up to 20%without impairing the execution of veer or gybe maneuvers.

According to the present invention, batten 10 allows optimum control ofthe deformation of the surface of sail 1 during the above directionchange maneuvers.

In fact, batten 10 exhibits the advantageous feature of having apredetermined value of bending stiffness based on the working pressureat which it is inflated, such value considerably decreasing, for anincrease of the bending load on batten 10 beyond a predetermined value,up to become substantially null when the bending load exceeds apredetermined threshold value. The threshold value of the bending loadis function of the inflating pressure of batten 10, of the diameterthereof and of the elasticity modulus of the materials forming thebatten.

As already indicated, the decrease of the bending stiffness of batten 10as the bending load increases is such as to reach a value comprisedbetween 0.01% and 50% of the above predetermined value.

The Applicant has noted that for decreases of the bending stiffness ofthe batten as the load changes that are close to the lower limit of theabove range, that is, close to 0.01% of the above predetermined value,the sailing boat is particularly suitable for races where there arefrequent changes of direction, such as in America's Cup match races.

The Applicant has further noted that for decreases of the bendingstiffness of the batten as the load changes that are close to the upperlimit of the above range, that is, close to 50% of the abovepredetermined value, the sailing boat is particularly suitable for raceswhere there are no frequent changes of direction, such as in oceanraces.

Preferably, the decrease of the bending stiffness of batten 10 as thebending load increases is such as to reach a value comprised between0.01% and 30% of the above predetermined value. Even more preferably,the decrease of the bending stiffness of batten 10 as the bending loadincreases is such as to reach a value comprised between 0.01% and 10% ofthe above predetermined value. Even more preferably, the decrease of thebending stiffness of batten 10 as the bending load increases is such asto reach a value comprised between 0.01% and 5% of the abovepredetermined value.

As already mentioned, the predetermined value of bending stiffness withno bending load is preferably comprised between about 10 Nm² and about100 Nm².

As already mentioned, the working pressure of battens 10 is preferablycomprised between about 5 bar and about 50 bar. Preferably, the aboveworking pressure is comprised between about 15 bar and about 50 bar forbattens with a diameter comprised between about 20 mm and about 35 mm,and between about 5 bar and about 30 bar for battens with a diametercomprised between about 35 mm and about 70 mm.

The preferred use of batten 10 of the present invention is in the genoaof racing sailing boats, where the direction change maneuvers arerequired to be carried out as quickly as possible without impairing theboat speed.

FIGS. 4 a-4 d show a sail 1, similar to that of FIG. 1, in a racingsailing boat, indicated with reference numeral 100, in four differentsteps of a race. As already said, the sail in particular is a genoa.There are also shown a mainsail 20, provided with battens 30 that may besimilar to battens 10 of the present invention, and the mast 50 of thesailing boat.

In particular, FIG. 4 a shows the position of the genoa prior to thedirection change manoeuvre, whereas FIG. 4 d shows the position of thegenoa at the end of such manoeuvre. It can be seen that at the beginningof the manoeuvre (FIG. 4 a), the genoa is entirely arranged on one sideof boat 100 relative to mast 50, while at the end of the manoeuvre (FIG.4 d), the genoa has entirely passed to the opposite side of boat 100relative to the mast. FIGS. 4 b and 4 c show the genoa while it movesfrom one side to the other of mast 50 (in particular, note the topportion of the after leech).

During execution of the direction change manoeuvre, battens 10 hitagainst the equipment of mast 50 and bend to allow the genoa to pass tothe opposite side of the mast.

In particular, as the bending load increases by the effect of the thrustagainst the equipment of mast 50 and after exceeding a certain criticalvalue of the bending stress (such value depending on the battendiameter, on the inflating pressure and on the elastic modulus of thematerial forming the batten itself), the bending stiffness of batten 10considerably decreases, until batten 10 collapses in one or more points,thus almost completely losing its stiffness and passing beyond mast 50almost without any resistance. Once moved beyond mast 50, battenimmediately resumes its initial stiffness and immediately stretches.

The Applicant has carried out a series of experimental tests on battensmade in accordance with the present invention. In particular, battenswith a thickness equal to 2.5 mm, of various diameters and inflated atdifferent pressure values, were manufactured. Such battens weresubjected to an increasing bending load according to the schemeillustrated in FIG. 7 and the deflection stiffness values were recorded(vertical arrow according to the above scheme) by an automaticacquisition system. By applying the formula:

EJ=FL ³/48D

where:EJ=bending stiffness;D=camber or deflection;F=applied load; andL=distance between the supports;the variation of the bending stiffness as a function of the applied loadwas obtained.

The result of such experimental tests is shown in the graphs of FIGS. 5and 6. In such graphs, the values of the bending load the battens weresubjected to are indicated on the abscissa axis, whereas the values ofthe measured bending stiffness are indicated on the ordinate axis.

In particular, FIG. 5 shows the result of three experimental testscarried out on three battens manufactured according to the preferredembodiment of the present invention. Curve a is representative of abatten having an inner diameter equal to 30 mm, inflated at a pressureof 20 bar and whose reinforcing structure consists of a first layer ofreinforcing thread-like elements arranged along a substantiallycircumferential direction and of a second layer, overlapped to the firstlayer, of reinforcing thread-like elements arranged along asubstantially longitudinal direction, that is, in the above reinforcingstructure the cross angle between the reinforcing thread-like elementsis substantially a right angle. Curve b is representative of a battenhaving an inner diameter equal to 22 mm, inflated at a pressure of 25bar and whose reinforcing structure is identical to that of the battenof curve a. Curve c represents a batten having an inner diameter equalto 17 mm, inflated at a pressure of 25 bar and whose reinforcingstructure is identical to that of the batten of curve a.

The three curves of the graph of FIG. 5 show how, for each of thebattens used in the experimental tests carried out by the Applicant, asthe bending load increases the bending stiffness of the battenprogressively decreases until, at a threshold value of the bending load,the bending stiffness of the batten falls down to a substantially nullvalue. The lower end of each curve indicates the value of the bendingstiffness at which the above downfall of the bending stiffness occurs.The batten collapses at such value. It can be seen that for the battenwith a diameter of 30 mm inflated at 20 bar (curve a), the bendingstiffness decreases by about 10% for loads up to about 65 N, to thenreach the collapse point at about 88 N. In the range of loads up to 65N, the batten therefore imparts to the sail the stiffness features(bending stiffness values comprised between about 50 Nm² and about 56Nm²) adapted for collecting the wind thrust. After the collapse isoccurred, the bending stiffness quickly decreases to negligible values.Similarly, for the batten with an inner diameter of 22 mm inflated at 25bar (curve b), the bending stiffness decreases by about 10%, changingfrom the value of about 25 Nm² to the value of about 22 Nm², for loadsup to about 30 N, to then reach the collapse point at about 40 N. Afterthe collapse is occurred, the bending resistance quickly decreases tonegligible values. For the batten with an inner diameter of 17 mminflated at 25 bar (curve c), the bending stiffness decreases by about10%, changing from the value of about 22 Nm² to the value of about 20Nm², for loads up to about 20 N, to then reach the collapse point atabout 33 N.

The curves in the graph of FIG. 5 further show how the bending stiffnessof the batten increases as the diameter increases.

FIG. 6, on the other hand, shows a graph relating to the variation ofthe bending stiffness based on the bending load, wherein there are shownthe bending stiffness values based on the load of the batten of curve aand of a batten manufactured according to an optional embodiment of thepresent invention (curve d). In particular, this is a batten thatdiffers from that of curve a only in that the top layer of reinforcingthread-like elements, rather than comprising reinforcing thread-likeelements arranged along a substantially longitudinal direction (as inthe case of the batten of curve a), comprises reinforcing thread-likeelements arranged along respective paths inclined by an angle of 15°relative to the longitudinal direction (FIG. 3 a).

It can be seen that for this latter batten (curve d), the bendingstiffness decreases by about 20% for loads up to about 65 N, to thenreach the collapse point at about 88 N. After the collapse is occurred,the bending stiffness quickly decreases, also in this case, tonegligible values. By comparing curve a with curve d it is possible tosee that the presence of a layer of substantially circumferentialreinforcing thread-like elements and of a layer of substantiallylongitudinal circumferential reinforcing thread-like elements isadvantageous, as compared to the case of a layer of reinforcingthread-like elements inclined by 15° relative to the longitudinaldirection, since stronger bending stiffness is obtained up to loadsclose to the critical load that makes the batten structure unstable.

Finally, by shaping cap 40 b carrying valve 47 as illustrated in FIG. 2,it is possible to obtain a system adapted for anchoring battens 10 intopockets 3 of sail 1, preferably by a closing tape provided in eachpocket 3 that fit into a recess of cap 40 b.

1. A method for controlling the deformation of a surface of a sail (1)of a sailing boat (100) during a direction change manoeuvre, said methodcomprising the steps of: arranging at least one inflatable batten (10)into a respective seat (3) obtained on a side surface (2 a) of a sail(1) of a sailing boat (100), said at least one inflatable batten (10)being inflated at such a pressure as to impart to said at least oneinflatable batten (10) a bending stiffness having, with no bending load,a predetermined value; carrying out a direction change manoeuvre of thesailing boat (100), wherein in a first part of said manoeuvre said atleast one batten (10) is subjected to the action of an increasingbending load and in a second part of said manoeuvre said bending loadends its action on said at least one batten (10), during said manoeuvrethe mechanical properties of said at least one batten being modified sothat as said bending load increases in said first part of the manoeuvre,the value of the bending stiffness of said at least one batten (10)decreases considerably and as said bending load ends its action in saidsecond part of the manoeuvre, the bending stiffness of said at least onebatten (10) returns to said predetermined value.
 2. A method accordingto claim 1, wherein the value of said bending stiffness decreases to becomprised between about 0.01% and about 50% of said predetermined value.3. A method according to claim 1, wherein the value of said bendingstiffness decreases to be comprised between about 0.01% and about 30% ofsaid predetermined value.
 4. A method according to claim 1, wherein thevalue of said bending stiffness decreases to be comprised between about0.01% and about 10% of said predetermined value.
 5. A method accordingto claim 1, wherein the value of said bending stiffness decreases to becomprised between about 0.01% and about 5% of said predetermined value.6. A method according to claim 1, wherein for a bending load higher thana predetermined threshold value, the bending stiffness of said at leastone batten (10) is substantially null.
 7. A method according to any oneof the previous claims, wherein said predetermined value of bendingstiffness with no bending load is comprised between about 10 Nm² andabout 100 Nm².
 8. A method according to any one of the previous claims,wherein said batten (10) is inflated at an operating pressure comprisedbetween about 5 bar and about 50 bar.
 9. A method according to claim 8,wherein said working pressure is comprised between about 15 bar andabout 50 bar for battens with an inner diameter comprised between about20 mm and about 35 mm.
 10. A method according to claim 8, wherein saidworking pressure is comprised between about 5 bar and about 30 bar forbattens with a diameter comprised between about 35 mm and about 70 mm.11. A method according to any one of the previous claims, wherein saidat least one batten (10) comprises a reinforcing structure (33)comprising a plurality of reinforcing thread-like elements (34 a, 34 b)arranged crossed to one another.
 12. A method according to claim 11,wherein the above reinforcing thread-like elements (34 a, 34 b) arearranged crossed at a predetermined angle comprised between about 65°and about 115°.
 13. A method according to claim 11, wherein the abovereinforcing thread-like elements (34 a, 34 b) are arranged crossed at apredetermined angle comprised between about 70° and about 110°.
 14. Amethod according to claim 11, wherein the above reinforcing thread-likeelements (34 a, 34 b) are arranged crossed at a predetermined anglecomprised between about 80° and about 100°.
 15. A method according toclaim 11, wherein the above reinforcing thread-like elements (34 a, 34b) are arranged crossed at a predetermined substantially right angle.16. A method according to any one of the previous claims, wherein saidat least one batten (10) comprises a fluid impervious wrapping (31)containing a fluid at a working pressure.
 17. A method according toclaim 16, wherein a reinforcing structure (33) is associated with saidfluid impervious wrapping (31).
 18. A method according to claim 17,wherein said reinforcing structure (33) is external to said fluidimpervious wrapping (31).
 19. A method according to any one of claimsfrom 11 to 18, wherein said reinforcing structure (33) is closed at theends of said batten (10).
 20. A sail (1) for sailing boats (100),comprising: at least one seat (3) for a respective batten (10); at leastone inflatable batten (10) housed into said at least one seat (3), saidat least one inflatable batten (10) comprising: a fluid imperviouswrapping (31) containing a fluid under pressure, said fluid being atsuch pressure as to impart a bending stiffness to said at least onebatten (10) having, with no bending load, a predetermined value; areinforcing structure (33) associated with said wrapping (31) andcomprising a plurality of reinforcing thread-like elements (34 a, 34 b)arranged crossed to each other; said at least one batten (10) being suchthat, when subjected to an increasing bending load, the bendingstiffness thereof decreases considerably and when said bending load endsits action, the bending stiffness thereof returns to said predeterminedvalue.
 21. A sail (1) according to claim 20, wherein the abovereinforcing thread-like elements (34 a, 34 b) are arranged crossed at apredetermined angle comprised between about 65° and about 115°.
 22. Asail (1) according to claim 20, wherein the above reinforcingthread-like elements (34 a, 34 b) are arranged crossed at apredetermined angle comprised between about 70° and about 110°.
 23. Asail (1) according to claim 20, wherein the above reinforcingthread-like elements (34 a, 34 b) are arranged crossed at apredetermined angle comprised between about 80° and about 100°.
 24. Asail (1) according to claim 20, wherein the above reinforcingthread-like elements (34 a, 34 b) are arranged crossed at apredetermined substantially right angle.
 25. A sail (1) according to anyone of claims from 20 to 24, wherein said reinforcing structure (33)comprises a layer comprising first reinforcing thread-like elements (34a) arranged along a first direction and second reinforcing thread-likeelements (34 b) arranged along a second direction inclined, relative tosaid first direction, by said predetermined angle.
 26. A sail (1)according to any one of claims from 20 to 24, wherein said reinforcingstructure (33) comprises two overlapped layers (33 a, 33 b) ofreinforcing thread-like elements, a first layer (33 a) comprising firstreinforcing thread-like elements (34 a) arranged along a first directionand a second layer (33 b) comprising second reinforcing thread-likeelements (34 b) arranged along a second direction inclined, relative tosaid first direction, by said predetermined angle.
 27. A sail (1)according to claim 25 or 26, wherein said second reinforcing thread-likeelements (34 b) are arranged parallel to one another along asubstantially longitudinal direction of said batten (10).
 28. A sail (1)according to claim 25 or 26, wherein said second reinforcing thread-likeelements (34 b) extend along respective paths having an angle ofinclination comprised between about +20° and about −20° relative to alongitudinal direction of said batten (10).
 29. A sail (1) according toclaim 25 or 26, wherein said first reinforcing elements (34 a) arearranged parallel to one another along a substantially circumferentialdirection of said batten (10).
 30. A sail (1) according to claim 25 or26, wherein said first reinforcing thread-like elements (34 a) extendalong respective paths having an angle of inclination comprised betweenabout +5° and about −5° relative to a circumferential direction of saidbatten (10).
 31. A sail (1) according to any one of claims from 26 to30, wherein said second layer (33 b) is arranged outside said firstlayer (33 a).
 32. A sail (1) according to any one of claims from 20 to31, wherein said reinforcing thread-like elements (34 a, 34 b) comprisecords made of kevlar.
 33. A sail (1) according to any one of claims from20 to 32, wherein said reinforcing thread-like elements (34 a, 34 b) areincorporated in a vulcanised elastomeric material.
 34. A sail (1)according to any one of claims from 20 to 33, wherein said at least onebatten (10) further comprises, at a first end (10 a) thereof, a firstclosing cap (40 a).
 35. A sail (1) according to any one of claims from20 to 34, wherein said at least one batten (10) comprises, at a secondend (10 b) thereof, a second closing cap (40 b) comprising aninflating/deflating valve (47).
 36. A sail (1) according to claims 34and 35, wherein said first and second closing caps (40 a, 40 b) comprisea tubular sleeve (41 a, 41 b) sealingly coupled to an inner surface ofsaid fluid impervious wrapping (31).
 37. A sail (1) according to claim36, wherein said tubular sleeve (41 a, 41 b) comprises a first sealinglip (43 a, 43 b) in abutment against a front end surface of said fluidimpervious wrapping (31) and a tubular collar (42 a, 42 b) sealinglycoupled to an outer surface of said reinforcing structure (33) and tosaid sleeve (41 a, 41 b).
 38. A sail (1) according to claim 36, whereinsaid inflating/deflating valve (47) is associated with a front surface(44 b) of said sleeve (41 b), said sleeve (41 b) further comprising aprotection lip (49) for said inflating/deflating valve (47).
 39. A sail(1) according to claim 38, wherein said protection lip (49) comprises atapered side surface (490).
 40. A sail (1) according to any one ofclaims from 20 to 39, wherein said at least one batten (10) has asubstantially tubular shape with a circular section substantiallyconstant along the entire longitudinal extension thereof.
 41. A sail (1)according to any one of claims from 20 to 39, wherein said at least onebatten (10) has a substantially cylindrical shape with at least one conetapered end.
 42. A sail (1) according to claims 34 and 35, wherein thereinforcing thread-like elements (34 a, 34 b) are connected to the abovefirst (40 a) and second (40 b) closing caps.
 43. A sail (1) according toclaims 34 and 35, wherein the second reinforcing thread-like elements(34 b) are connected to the above first (40 a) and second (40 b) closingcaps.
 44. A sail (1) according to any one of claims from 20 to 43,wherein said predetermined value of bending stiffness with no bendingload is comprised between about 10 Nm² and about 100 Nm².
 45. A sail (1)according to any one of claims from 20 to 44, wherein said batten (10)is inflated at an operating pressure comprised between about 5 bar andabout 50 bar.
 46. A sail (1) according to any one of claims from 20 to45, wherein said reinforcing structure (33) is external to said fluidimpervious wrapping (31).
 47. A sail (1) according to any one of claimsfrom 20 to 46, wherein said sail is a genoa or a mainsail.
 48. A batten(10) for sails (1) of a sailing boat (100), comprising: a fluidimpervious wrapping (31) adapted to be inflated by a fluid underpressure, wherein such fluid under pressure imparts a bending stiffnessto said batten (10), said bending stiffness having, with no bendingload, a predetermined value; a reinforcing structure (33) associatedwith said wrapping (31) and comprising a plurality of reinforcingthread-like elements (34 a, 34 b) arranged crossed at a predeterminedangle comprised between about 65° and about 115°; wherein, when saidwrapping (31) is inflated at said working pressure and said batten (10)is subjected to an increasing bending load, the bending stiffnessthereof decreases considerably and when said bending load ends itsaction, the bending stiffness thereof returns to said predeterminedvalue.
 49. A batten (10) according to claim 48, wherein saidpredetermined angle is comprised between about 70° and about 110°.
 50. Abatten (10) according to claim 48, wherein said predetermined angle iscomprised between about 80° and about 100°.
 51. A batten (10) accordingto claim 48, wherein said predetermined angle is substantially a rightangle.
 52. A batten (10) according to any one of claims from 48 to 51,wherein said reinforcing structure (33) comprises a layer comprisingfirst reinforcing thread-like elements (34 a) arranged along a firstdirection and second reinforcing thread-like elements (34 b) arrangedalong a second direction inclined, relative to said first direction, bysaid predetermined angle.
 53. A batten (10) according to any one ofclaims from 48 to 51, wherein said reinforcing structure (33) comprisestwo overlapped layers (33 a, 33 b) of reinforcing thread-like elements(34 a, 34 b), a first layer (33 a) comprising first reinforcingthread-like elements (34 a) arranged along a first direction and asecond layer (33 b) comprising second reinforcing thread-like elements(34 b) arranged along a second direction inclined, relative to saidfirst direction, by said predetermined angle.
 54. A batten (10)according to claim 52 or 53, wherein said second reinforcing thread-likeelements (34 b) are arranged parallel to one another along asubstantially longitudinal direction of said batten (10).
 55. A batten(10) according to claim 52 or 53, wherein said second reinforcingthread-like elements (34 b) extend along respective paths having anangle of inclination comprised between about +20° and about −20°relative to a longitudinal direction of said batten (10).
 56. A batten(10) according to claim 52 or 53, wherein said first reinforcingthread-like elements (34 a) are arranged parallel to one another along asubstantially circumferential direction of said batten (10).
 57. Abatten (10) according to claim 52 or 53, wherein said first reinforcingthread-like elements (34 a) extend along a direction having an angle ofinclination comprised between about +5° and about −5° relative to acircumferential direction of said batten (10).
 58. A batten (10)according to any one of claims from 53 to 57, wherein said second layer(33 b) is arranged outside said first layer (33 a).
 59. A batten (10)according to any one of claims from 48 to 58, wherein said reinforcingthread-like elements (34 a, 34 b) comprise cords made of kevlar.
 60. Abatten (10) according to any one of claims from 48 to 59, wherein saidreinforcing thread-like elements (34 a, 34 b) are incorporated in avulcanised elastomeric material.
 61. A batten (10) according to any oneof claims from 48 to 60, further comprising a first closing cap (40 a)at a first end (10 a) thereof.
 62. A batten (1) according to any one ofclaims from 48 to 61, further comprising a second closing cap (40 b) ata second end (10 b) thereof, comprising an inflating/deflating valve(47).
 63. A batten (10) according to claims 61 and 62, wherein saidfirst and second closing caps (40 a, 40 b) comprise a tubular sleeve (41a, 41 b) sealingly coupled to an inner surface of said fluid imperviouswrapping (31).
 64. A batten (10) according to claim 63, wherein saidtubular sleeve (41 a, 41 b) comprises a first sealing lip (43 a, 43 b)in abutment against a front end surface of said fluid imperviouswrapping (31) and a tubular collar (42 a, 42 b) sealingly coupled to anouter surface of said reinforcing structure (33) and to said sleeve (41a, 41 b).
 65. A batten (10) according to claim 63, wherein saidinflating/deflating valve (47) is associated with a front surface (44 b)of said sleeve (41 b), said sleeve (41 b) further comprising aprotection lip (49) for said inflating/deflating valve (47).
 66. Abatten (10) according to claim 65, wherein said protection lip (49)comprises a tapered side surface (490).
 67. A batten (10) according toany one of claims from 48 to 66, wherein said batten (10) has asubstantially tubular shape with a circular section substantiallyconstant along the entire longitudinal extension thereof.
 68. A batten(10) according to any one of claims from 48 to 66, wherein said batten(10) has a substantially cylindrical shape with at least one conetapered end.
 69. A batten (10) according to claims 61 and 62, whereinthe reinforcing thread-like elements (34 a, 34 b) are connected to theabove first (40 a) and second (40 b) closing caps.
 70. A batten (10)according to claims 61 and 62, wherein the second reinforcingthread-like elements (34 b) are connected to the above first (40 a) andsecond (40 b) closing caps.
 71. A batten (10) according to any one ofclaims from 48 to 70, wherein said predetermined value of bendingstiffness with no bending load is comprised between about 10 Nm² andabout 100 Nm².
 72. A batten (10) according to any one of claims from 48to 71, wherein said batten (10) is inflated at an operating pressurecomprised between about 5 bar and about 50 bar.
 73. A batten (10)according to any one of claims from 48 to 72, wherein said reinforcingstructure (33) is external to said fluid impervious wrapping (31).